In various industries, granular material of various consistencies is stored in a solids container. Ordinarily, the particulate material is loaded into the container through the upper end thereof and is withdrawn from the container through its lower end.
If the solids container is used to continuously feed a given amount of a granular material into some receptacle, it is highly desirable to know when the container is full and/or when the container is empty. Many methods for determining the filling and feeding status of a granular material into and out of a solids container, respectively, have been proposed. Examples of these methods range from visual observations to highly sophisticated electrical sensors. Most of these methods, however, have inherent problems associated therewith. For example, visually observing the level of granular material being fed into a solids container lacks uniformity. This problem can result in either underfilling or overfilling the chosen receptacle. Electronic sensors, on the other hand, generally result in mechanical problems due to the high concentrations of dust resulting from filling the solids container.